4-pyridazinecarboxamides and esters as interleukin-1β  converting enzyme inhibitors

ABSTRACT

Disclosed are compounds of the formula (I) and pharmaceutically acceptable salts thereof:                  
 
wherein
         R 1  is a halogen, or an oxygen linked leaving group including an aromatic ether, an alkyl sulfonate, an aryl sulfonate, an alkyl phosphonate, an aryl phosphonate, an alkyl phosphate or aryl phosphate;   R 2  is COOR 5 , C(═O)NH(CHR 5 ) m —COOR 5 , NH(CHR 5 ) m CON(R 5 )R 6 , C(═O)N(R 5 )R 6  or NH(CHR 5 ) m OH;   R 3  is H or alkyl;   R 4  is H, substituted or unsubstituted aryl, heteroaryl or alkyl;   R 5  and R 6  are independently H, lower alkyl, aryl, hydroxy alkyl, amino alkyl, heteroaryl, lower alkylene-aryl, lower alkylene-heteroaryl or lower cycloalkyl; and m=0–6; pharmaceutical compositions containing the compounds; and a method for inhibiting interleukin-1β protease activity in a mammal utilizing the compounds and compositions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.08/625,680, filed Apr. 3, 1996, now U.S. Pat. No. 6,624,166, which is acontinuation of U.S. patent application Ser. No. 08/452,767, filed May30, 1995, now abandoned, which is a continuation of U.S. patentapplication Ser. No. 08/073,914, filed Jun. 8, 1993, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a series of novel pyridazine analogs whichexhibit selective inhibition of interleukin-1β converting enzyme, tocompositions containing the novel pyridazine analogs and methods fortherapeutic utility. More particularly, the interleukin-1β convertingenzyme inhibitors described in this invention comprise novel pyridazineanalogs which possess particular utility in the treatment ofinflammatory, immune-based diseases and cancer.

2. Reported Developments

Interleukin-1β protease (also known as interleukin-1β converting enzymeor ICE) is the enzyme responsible for processing of the biologicallyinactive 31 kD precursor IL-1β to the biologically active 17 kD form(Kostura, M. J.; Tocci, M. J.; Limjuco, G.; Chin, J.; Cameron, P.;Hillman, A. G.; Chartrain, N. A.; Schmidt, J. A. Proc. Nat. Acad. Sci.,1989, 86, 5227–5231 and Black, R. A.;, Kronheim, S. R.; Sleath, P. R.FEBS Let., 1989, 247, 386–391). In addition to acting as one of thebody's early responses to injury and infection, IL-1β has also beenproposed to act as a mediator of a wide variety of diseases, includingrheumatoid arthritis, osteoarthritis, inflammatory bowel disease,sepsis, and acute and chronic myelogenous leukemia (Dinarello, C. A.;Wolff, S. M., New Engl. J. Med., 1993, 328, 106). The naturallyoccurring IL-1β receptor antagonist has been used to demonstrate theintermediacy of IL-1β in a number of human diseases and animal models(Hannum, C. H.; Wilcox, C. J.; Arend, W. P.; Joslin, G. G.; Dripps, D.J.; Heimdal, P. L.; Armes, L. G.; Sommer, A.; Eisenberg, S. P.;Thompson, R. C., Nature, 1990, 343, 336–340; Eisenberg, S. P.; Evans, R.J.; Arend, W. P.; Verderber, E.; Brewer, M. T.; Hannum, C. H.; Thompson,R. C., Nature 1990, 343, 341–346; Ohlsson, K.; Bjork, P.; Bergenfeldt,M.; Hageman, R.; Thompson, R. C., Nature, 1990, 348, 550–552; andWakabayashi, G., FASEB, 1991, 338–343). The specific role of IL-1β ininflammation and immunomodulation is supported by the recent observationthat the cowpox virus employs an inhibitor of ICE to suppress theinflammatory response of its host (Ray, C. A. et al, Cell, 1992, 69,597–604).

The present invention also relates to the modulation of processing ofIL-1β for the treatment of rheumatoid arthritis. Levels of IL-1β areknown to be elevated in the synovial fluid of patients with the disease.Additionally, IL-1β stimulates the synthesis of enzymes believed to beinvolved in inflammation, such as collagenase and PLA₂, and producesjoint destruction which is very similar to rheumatoid arthritisfollowing intra-articular injection in animals.

ICE is believed to be a cysteine protease (Thornbury, N. A. et al,Nature, 1992, 356–768). Peptidyl methyl ketone analogs constitute awell-known class of compounds having cysteine protease inhibitoryactivity. (D. Rich in Chapter 4 of “Proteinase Inhibitors”, Barrett, A.J. and Salvensen, G., eds., Elsevier, 1986). However, there has neverbeen a reported example of a non-peptide heterocyclic inhibitor of acysteine protease. Hence, the inhibitory activity displayed by thepyridazine analogs described herein against ICE is unique.

An effective therapy has yet to be developed for the treatment of IL-1βmediated inflammatory diseases. Consequently, there is a need fortherapeutic agents effective in the treatment and prevention of thesediseases.

SUMMARY OF THE INVENTION

In accordance with the present invention, novel non-peptidic pyridazinesare provided having the formula (I) and a pharmaceutically acceptablesalt thereof

wherein

-   -   R₁ is a halogen, or an oxygen linked leaving group including an        aromatic ether, an aromatic ester, an alkyl sulfonate, an aryl        sulfonate, an alkyl phosphonate, an aryl phosphonate, an alkyl        phosphate or aryl phosphate;    -   R₂ is OR₅, NH(CHR₅)_(m)—COOR₅, NH(CHR₅)_(m)CON(R₅)R₆, N(R₅)R₆ or        NH(CHR₅)_(n)OH;    -   R₃ is H or alkyl;    -   R₄ is H, substituted or unsubstituted aryl, heteroaryl or alkyl;    -   R₅ and R₆ are independently H, lower alkyl, aryl, heteroaryl,        aralkyl, heteroaralkyl or lower cycloalkyl;    -   m=1–6; and    -   n=2–6.

As used herein, the term pharmaceutically acceptable salts includes theacid and base addition salts.

The term acid addition salts refers to those salts which retain thebiological effectiveness and properties of the free bases and which arenot biologically or otherwise undesirable, formed with inorganic acidssuch as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid,phosphoric acid and the like, and organic acids such as acetic acid,propionic acid, glycolic acid, pyruvic acid, oxalic acid, maleic acid,malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid,benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid,ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid and thelike.

The term base addition salts include those derived from inorganic basessuch as sodium, potassium, lithium, ammonium, calcium, magnesium, iron,zinc, copper, manganese, aluminum salts and the like. Particularlypreferred are the ammonium, potassium, sodium, calcium and magnesiumsalts derived from pharmaceutically acceptable organic non-toxic basesinclude salts of primary, secondary, and tertiary amines, substitutedamines including naturally occurring substituted amines, cyclic aminesand basic ion exchange resins, such as isopropylamine, trimethylamine,diethylamine, triethylamine, tripropylamine, ethanolamine,2-dimethylaminoethanol, 2-diethylaminoethanol, trimethamine,dicyclohexylamine, lysine, arginine, histidine, caffeine, procaines,hydrabamine, choline, betaine, ethylenediamine, glucosamine,methylglucamine, theobromine, purines, piperazine, piperidine,N-ethylpiperidine, polyamine resins and the like. Particularly preferredorganic non-toxic bases are isopropylamine, diethylamine, ethanolamine,trimethamine, dicyclohexylamine, choline and caffeine.

“Alkyl” is defined as a saturated or unsaturated aliphatic hydrocarbonwhich may be either straight- or branched-chain. Preferred groups haveno more than about 12 carbon atoms and may be methyl, ethyl andstructural isomers of propyl, butyl, pentyl, hexyl, heptyl, octyl,nonyl, decyl, undecyl and dodecyl.

“Lower alkyl” is defined as an alkyl group as above, having 1 to 4carbon atoms. Suitable lower alkyl groups are methyl, ethyl, n-propyl,isopropyl, butyl, tert-butyl, n-pentyl, neopentyl, n-hexyl, andn-heptyl.

“Lower cycloalkyl” is defined as a carbocyclic ring of 3–8 carbon atomsincluding cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.

“Aryl” is defined as phenyl, naphthyl and substituted phenyl.

“Substituted phenyl” is defined as a phenyl group in which one or moreof the hydrogens has been replaced by the same or different substituentsincluding halo, lower alkyl, nitro, amino, acylamino, hydroxyl, loweralkoxy, aryl, heteroaryl, alkyl sulfonyl, arylsulfonamido,trifluoromethyl, morpholinoethoxy and morpholino-sulfonyl, andcarbobenzoxy-methyl sulfamoyl.

“Halogen” is defined as chloride, fluoride, bromide or iodide.

“Heteroaryl” is defined as pyridyl, thienyl, furyl, thiazolyl,imidazolyl, pyrazolyl, triazinyl, quinolyl, and isoquinolyl.

“Substituted heteroaryl” means a heteroaryl group in which one or moreof the hydrogens has been replaced by the the same or differentsubstituents including halo, lower alkyl, nitro, amino, acylamino,hydroxyl, lower alkoxy, aryl, heteroaryl, lower alkoxy, alkylsulfonyl,trifluoromethyl, morpholinoethoxy, morpholino-sulfonyl,carbobenzoxy-methylsulfamoyl.

“Aralkyl” is defined as an alkyl group susbstituted by an aryl ring. Forexample, benzyl, phenethyl and 4-chlorobenzyl.

The present invention concerns a method for inhibiting ICE in a mammalby administering a therapeutically effective amount of a compound of theFormula (I) or a pharmaceutical composition containing a compound of theFormula (I) in a pharmaceutically acceptable carrier. The method ofinhibition is directed for the treatment of IL-1β mediated, diseasestates or disorders which include: infectious diseases, such asmeningitis and salpingitis; septic shock, respiratory diseases;inflammatory conditions, such as arthritis, cholangitis, colitis,encephalitis, endocerolitis, hepatitis, pancreatitis and reperfusioninjury, immune-based diseass, such as hypersensitivity; auto-immunediseases, such as multiple sclerosis; bone diseases; and certain tumors.

The pharmaceutical composition of the present invention comprises anactive ingredient of the compound of formula (I) in admixture with apharmaceutically acceptable, non-toxic carrier. Such compositions may beprepared for use for parenteral (subcutaneous, intraarticular,intramuscular or intravenous) administration, particularly in the formof liquid solutions or suspensions; for oral or buccal administration,particularly in the form of tablets or capsules; or intranasally,particularly in the form of powders, nasal drops or aerosols.

When administered orally (or rectally) the compounds will usually beformulated into a unit dosage form such as a tablet, capsule,suppository or cachet. Such formulations typically include a solid,semi-solid or liquid carrier or diluent. Exemplary diluents and vehiclesare lactose, dextrose, sucrose, sorbitol, mannitol, starches, gumacacia, calcium phosphate, mineral oil, cocoa butter, oil of theobroma,alginates, tragacanth, gelatin, syrup, methylcellulose, polyoxyethylenesorbitan monolaurate, methyl hydroxybenzoate, propyl hydroxybenzoate,talc, and magnesium stearate.

The compositions may be prepared by any of the methods well-known in thepharmaceutical art, for example as described in Remington'sPharmaceutical Sciences, 17th edition, Mack Publishing Company, Easton,Pa., 1985. Formulations for parenteral administration may contain ascommon excipients sterile water or saline, alkylene glycols such aspropylene glycol, polyalkylene glycols such as polyethylene glycol, oilsof vegetable origin, hydrogenated naphthalenes and the like. Examples ofvehicles for parenteral administration include water, aqueous vehiclessuch as saline, Ringer's solution, dextrose solution, and Hank'ssolution and nonaqueous vehicles such as fixed oils (such as corn,cottonseed, peanut, and sesame), ethyl oleate, and isopropyl myristate.Sterile saline is a preferred vehicle and the compounds are sufficientlywater soluble to be made up as a solution for all foreseeable needs. Thevehicle may contain minor amounts of additives such as substances thatenhance solubility, isotonicity, and chemical stability, e.g.,antioxidants, buffers, and preservatives. For oral administration, theformula can be enhanced by the addition of bile salts and also by theaddition acylcarnitines (Am. J. Physiol. 251:3332 (1986). Formulationsfor nasal administration may be solid and contain as excipients, forexample, lactose or dextran, or may be aqueous or oily solutions foradministration in the form of nasal drops or metered spray. For buccaladministration typical excipients include sugars, calcium stearate,magnesium stearate, pregelatinated starch, and the like.

When formulated for nasal administration the absorption across the nasalmucous membrane is enhanced by surfactant acids, such as for example,glycocholic acid, cholic acid, taurocholic acid, ethocholic acid,desoxycholic acid, chenodesoxycholic acid, dehydrocholic acid,glycodeoxycholic acid, and the like (See, B. H. Vickery, “LHRH and itsAnalogs-Contraception and Therapeutic Applications”, Pt.2, B. H. Vickeryand J. S. Nester, Eds., MTP Press, Lancaster, UK, 1987).

In general, for the uses as described in the present invention, it isexpedient to administer the active ingredient in amounts between about0.1 and 100 mg/kg body weight, most preferably from about 0.1 to 30mg/kg body weight for human therapy, the active ingredient will beadministered preferably in the range of from about 0.1 to about 20–50mg/kg/day. This administration may be accomplished by a singleadministration, by distribution over several applications or by slowrelease in order to achieve the most effective results. Whenadministered as a single dose, administration will most preferably be inthe range of from about 0.1 to 10 mg/kg of body weight.

The exact dose and regimen for administration of these compounds andcompositions will necessarily be dependent upon the needs of theindividual subject being treated, the type of treatment, and the degreeof affliction or need. In general, parenteral administration requireslower dosage than other methods of administration which are moredependent upon absorption.

DETAILED DESCRIPTION OF THE INVENTION

Compounds of the present invention are prepared according to Schemes I,II and III.

wherein

R₂ and R₃ are defined previously.

Referring to Scheme I, the condensation of a-keto esters with arylketones to provide 6-aryl-3-hydroxypyridazines has been previouslydescribed [Druey, J. and von Schmidt, P. (1954) Helv. Chim. Acta., Vol.37, 134]. Diethyl ketomalonate (1) and the aryl ketone (2) are heatedtogether neat to approximately 120° C. for 15 hours to provide thecondensation product (3). The keto-diester (3) is then treated withhydrazine in ethanol at reflux to form the 6-aryl-3-hydroxypyridazine(4), as crystalline solids. Saponification with aqueous alkali followedby neutralization provides the 3-hydroxy-carboxy-6-aryl-pyridazines (5).The conversion of 3-hydroxy-4-carboxy-6-aryl-pyridazines to theirdichlorides (6) has been previously described in U.S. Pat. No. 4,590,194and is performed by heating the pyridazines (5) with a halogenatingagent (phosphorus oxychloride being the preferred agent) at refluxtemperature (80° C.) for 4 hours. The halogenating agent may be usedneat or with inert solvent such as dioxane or toluene. The addition of acatalytic amount of DMF accelerates the reaction. Other suitablehalogenating agents include phenylphosphinic dichloride and phorphorustrichloride.

The corresponding 3-bromopyridazines are prepared similarly by heating(5) with phosphorous oxybromide or phosphorus tribromide. Thedichlorides (6) are isolated from the reaction mixture by removingexcess halogenating agent and solvent in vacuo and dissolving theresidue in hot acetonitrile or other polar inert solvent. The reactionof the dichlorides (6) in acetonitrile with alcohols or amines yield thedesired esters or amides (7).

Referring to Scheme II, intermediate ketomalonate addition products (2)can be prepared by deprotonatoin of the acetophenones (1) with lithiumdiisopropylamine (LDA) followed by the addition of ketomatonate. Thisprocedure was generally used for electron-rich aryl methyl ketones.

wherein R is phenyl, substituted aryl or heteroaryl.

Referring to Scheme III, the intermediate3,5-difluoro-4-(methylsulfonyl)-acetophenone (6) was prepared fromcommercially available 2,6-difluoroaniline. Bromination of the aniline(1) in acetic acid followed by diazotization and treatment of thediazonium salt with dimethylsulfide provides the thiomethyl derivative(3). Palladium catalyzed coupling reaction of (3) withtrimethylsilyacetylene yield arylacetylene (4).

Alkaline hydrolysis of the silyl group followed by mercuration andacidic solvolysis affords ketone (5). Oxidation of the ketone with Oxoneprovides the desired 3,5-difluoro-4-(methylsulfonyl)-acetophenone (6).

The following examples further illustrate the invention and are not tobe construed as limiting of the specification and claims in any way.

EXAMPLE 1 3-Chloro-4-carboxamido-6-(4-pyridyl)pyridazine

Diethyl ketomalonate (17.4 g, 0.1 mol) was heated with 4-acetylpyridine(12.1 g, 0.1 mol) at 120° C. for 15 h under nitrogen to provide diethyl2-hydroxy-2-(4-pyridyl)cabonylmethyl-malonate as a crystalline solid.The diester was refluxed in ethanol with a slight excess of hydrazinehydrate hydrochloride for 15 h to provide3-hydroxy-6-(4-pyridyl)-4-carbethoxy-pyridazine (4, Scheme 1). The aboveester was recrystallized from ethanol, hydrolyzed with aqueous sodiumhydroxide followed by careful neutralization with hydrochloric acid toafford 3-hydroxy-6-(4-pyridyl)-pyridazine-4-carboxylic acid (5, Scheme1). The acid was dissolved in phosphorous oxychloride containing acatalytic amount of DMF and the mixture was allowed to react at 80° C.for 4 h to provide 3-chloro-4-chlorocarbonyl-6-(4-pyridyl)pyridazine (6,Scheme 1) as a dark oil. the above dichloride was treated with gaseousammonia in acetonitrile to afford the title compound as a tan solid. Theabove dichloride was treated with excess gaseous ammonia to afford thetitle compound as a tan solid: ¹H NMR (DMSO-d6) δ 8.80 (d, J=6 Hz, 2H),8.59 (s, 1H), 8.20 (s, 1H), 8.17 (d, 6 Hz, 1H).

Utilizing appropriate starting materials and respects, and following theprocedures described in the Schemes and Example 1, the followingcompounds were prepared.

EXAMPLE 2 3-Chloro-4-carboethoxy-6-(4-pyridyl)pyridazine

The title compound was prepared by treating pyridazine dichloride withanhydrous ethanol and a slight excess of triethylamine. The titlecompound was purified via silica gel chromatography (20% ethylacetate/hexane). Anal. Calcd. for C₁₂H₁₀ClN₃O₂: C, 54.66; H, 3.82; N,15.94. Found: C, 54.07; H, 3.80; N, 15.83.

EXAMPLE 3 3-Chloro-4-carboxamido-6-(3-pyridyl)pyridazine

The title compound was prepared from 3-acetylpyridine. Anal. Calcd. forC₁₀H₇ClN₄O₂: C, 51.18; H, 3.09; N, 23.88. Found: C, 51.11; H, 3.09; N,23.98.

EXAMPLE 4 3-Chloro-4-carboxamido-6-(4-bromophenyl)pyridazine

The title compound was prepared from 4-bromoacetophenone. Anal. Calcd.for C₁₁H₇ClN₃O: C, 42.27; H, 2.26; N, 14.44. Found: C, 42.24; H, 2.19;N, 13.34.

EXAMPLE 5 3-Chloro-4-carboxamido-6-(4-trifluoromethylphenyl)pyridazine

The title compound was prepared from 4-trifluoromethyl-acetophenone.Anal. Calcd. for C₁₂H₇ClF₃N₃O: C, 47.78; H, 2.34; N, 13.92. Found: C,48.13; H, 2.14; N, 13.88.

EXAMPLE 6 3-Chloro-4-carboxamido-6-(3,5-dichlorophenyl)pyridazine

The title compound was prepared from 3,5-dichloroacetophenone. DCI-MSm/z 301.

EXAMPLE 7 3-Chloro-4-carboxamido-6-(2-naphthyl)pyridazine

The title compound was prepared from 2-acetonaphthone. DCI-MS m/z 283(M⁺).

EXAMPLE 8 3-Chloro-4-carboxamido-6-(4-nitrophenyl)pyridazine

The title compound was prepared from 4-nitroacetophenone. FAB-MS m/z,279(M+H+)

EXAMPLE 9 3-Chloro-4-carboxamido-6-(3-chloro-4-cyanophenyl)pyridazine

The title compound was prepared from 3-chloro-4-cyanoacetophenone.DCI-MS m/z 292.

EXAMPLE 10 3-Chloro-4-carboxamido-6-(2-pyrazyl)pyridazine

The title compound was prepared from 2-acetylpyrazine. DCI-MS m/z 236(M+H).

EXAMPLE 11 3-Chloro-4-carboxamido-5-methyl-6-(4-chlorophenyl)pyridazine

The title compound was prepared from 4-chloropropiophenone. DCI-MS m/z282 (m+H+). ¹H NMR (MeOD) δ 7.33 (s, 4H), 2.12 (s, 3H). Anal. Calcd. forC₁₂H₉Cl₂N₃O: C, 51.09; H, 3.22; N, 14.89. Found: C, 50.98; H, 3.34; N,14.48.

EXAMPLE 123-Chloro-4-(2,4-dichlorobenzylaminocarbonyl)-6-(4-pyridyl)pyridazine

The title compound was prepared by treating the dichloride (6) with2,4-dichlorobenzylamine according to Scheme I. DCI-MS m/z 392 (m+H+). ¹HNMR (CDCl₃) δ 8.83 (d, J=6 Hz, 2H), 8.33 (a, 1H), 8.00 (d, J=6 Hz, 2H),7.5 (m, 2H), 7.3 (m, 3H), 4.76 (d, J=6 Hz, 2H).

EXAMPLE 133-Chloro-4-[(C-ethoxy)glycyl]carbonyl)-6-(4-pyridyl)pyridazine

The title compound was prepared by treating the dichloride (6) withglycyl-ethyl ester according to Scheme I. DCI-MS m/z 320 (M+H). ¹H NMR(DMSO-d₆) δ 8.80 (d, J=6 Hz, 2H), 8.52 (s, 1H), 8.16 (d, J=6 Hz, 2H),4.13 (m, 4H), 1.22 (t, J=7.1 Hz, m, 3H).

EXAMPLE 143-Chloro-4-(2,4-dichlorobenzylaminocarbonyl)-6-[4-(3-chloro)pyridyl]-pyridazine

The title compound was prepared by reacting the dichloride (6) with2,4-dichlorobenzylamine according to Scheme I. Anal. Calcd. forC₁₇H₁₀Cl₄N₄O: C, 47.7; H, 2.35; N, 13.09. Found: C, 47.61; H, 2.25; N,13.06.

EXAMPLE 153-Chloro-4-carboxamido-6-[4-(p-toluenesulfonamido)phenyl]pyridazine

The title compound was prepared via catalytic hydrogenation of thep-nitrophenyl analog (5) of pyridazine followed by toluenesulfonylationand steps 4–5 according to Scheme I. DCI-MS m/z 402 (M+), 403 (mM+H).

EXAMPLE 16 3-Chloro-4-carboxamido-6-(4-quinolyl)pyridazine

The title compound was prepared from 4-acetylquinoline. ¹H NMR (MeOD) δ4.65 (s, 3H), 7.45 (m, 2H), δ 8.80 (d, J=6 Hz, 2H), 7.64 (m, 1H), 7.85(d, J=8.5 Hz, 1H), 7.93 (d, J=8.8 Hz, 1H), 7.96 (s, 1H), 8.79 (d, J=4.45Hz, 1H). The intermediate 4-acetylquinoline was prepared by treatment ofcommercially available 4-quinolinecarboxaldehyde with methylmagnesiumchloride in ether followed by oxidation of the resulting secondaryalcohol with manganese dioxide.

EXAMPLE 17 3-Chloro-4-carboxamido-6-(phenyl)pyridazine

A solution of acetophenone in THF at −70° C. was treated with a solutionof lithium diisopropylamide in THF (Scheme II). After 15 min diethylketomalonate was added and the reaction was allowed to warm to roomtemperature. The resulting condensation product 2 (Scheme II) was usedfollowing the procedure of Scheme I. DCI-MS m/z 233 (M+), 234 (M+H).

EXAMPLE 18 3-Chloro-4-carboxamido-6-(4-methoxyphenyl)pyridazine

The title compound was prepared from p-methoxyacetophenone in a manneranalogous to Example 17. DCI-MS m/z 263 (M+), 264 (M+H).

EXAMPLE 193-Chloro-4-carboxamido-6-[3,5-difluoro-4(methylsulfonyl))phenyl]pyridazine

The title compound was prepared from3,5-difluoro-4-(methylsulfonyl)-acetophenone according to Scheme I.Anal. Calcd. for C₁₂H₈ClF₂N₃O₃: C, 41.45; H, 2.32; N, 12.08. Found: C,41.19; H, 32.26; N. 12.03.

The intermediate 3,5-difluoro-4-(methylsulfonyl)acetophenone wasprepared from commercially available 2,6-difluoroaniline according toScheme III.

EXAMPLE 203-Chloro-4-carboxamido-6-[3-fluoro-4(methylsulfonyl)-5-(methoxy)-phenyl]-pyridazine

The title compound was prepared by refluxing3-chloro-4-carboxamido-6-[3,5-difluoro-4(methylsulfonyl)phenyl]pyridazinemade in Example 19 in methanol. DCI-MS m/z 359 (M+), 360 (M+H).

EXAMPLE 213-Chloro-4-[(phenylalanylcarbamido)-carbonyl]-6-(4-chlorophenyl)pyridazine

The title compound was prepared by treating the dichloride (6) withphenylalanine amide according to Scheme I. DCI-MS m/z 414 (M+), 415(M+H).

EXAMPLE 22 3-Chloro-4-carboxamido-6-(3-chloro-4-fluorophenyl)pyridazine

The title compound was prepared from 3-chloro-4-fluoro-acetophenone.DCI-MS m/z 286 (M+H+).

Compounds of the present invention were tested for IL-1β proteaseinhibition activity according to the following protocol:

-   -   Partially purified IL-1β protease is stored at −80° C. thawed on        ice, and preincubated for 10 minutes at 37° C. with 2.5 mM        dithiothreitol in a buffer solution containing 10 mM Tris-HCl        (pH 8.0) and 25% (v/v) glycerol. Inhibitors are prepared as        stock solutions in dimethyl sulfoxide (DMSO). The protease is        preincubated with inhibitor in a volume of 20 μL in a 1.5 mL        polypropylene microcentrifuge tube for 15 minutes at 37° C. The        volume of compound added to the assay is adjusted to yield a        DMSO concentration in the preincubation of <15% (v/v). The        enzyme assay is then initiated by the addition of substrate        (TRITC-AYVHDAPVRS-NH2) to yield a final concentration of 67 μM        in a final volume of 30 μL. The reactions are carried out for 60        minutes at 37° C. in the dark and are terminated by the addition        of 10 μL of 10% trifluoroacetic acid (TFA). Following the        addition of 115 μL of 0.1% TFA, the samples are analyzed by high        pressure liquid chromatography using a reverse phase (C18)        column and elution with an acetonitrile/water/TFA gradient.        Substrate and product are monitored by their absorbance at 550        nm and elute at 4.2 and 5.2 minutes, respectively.

The IL-1β protease inhibitory activity (IC50) for the pyridazine was<100 μM.

Although the invention has been described in the context of particularembodiments, it is intended that the scope of coverage of the patent notbe limited to those particular embodiments, but be determined byreference to the following claims.

1. A compound of the formula (I) or a pharmaceutically acceptable saltthereof:

wherein R₁ is halogen, alkyl sulfonate, aryl sulfonate, alkylphosphonate, aryl phosphonate, alkyl phosphate or aryl phosphate; R₂ isOR₅, NH(CHR₅)_(m)—COOR₅, N(R₅)R₆ or NH(CHR₅)_(m)OH; R₃ is H or alkyl; R₄is H, aryl, heteroaryl or alkyl, wherein said R₄ aryl is selected fromthe group consisting of substituted naphthyl, unsubstituted naphthyl,and substituted phenyl, and wherein the substituents of said R₄substituted phenyl are selected from the group consisting of halo, loweralkyl, nitro, amino, acylamino, hydroxy, lower alkoxy, alkyl sulfonyl,trifluoromethyl, morpholinoethoxy, morpholinosulfonyl andcarbobenzoxy-methyl sulfonyl; R₅ and R₆ are independently H, loweralkyl, aryl, hydroxy alkyl, amino alkyl, heteroaryl, loweralkylene-aryl, lower alkylene-heteroaryl or lower cycloalkyl; m is 0–6;and provided that when R₁ is chloro, R₃ is H and R₂ is NH₂, R₄ is not 3-or 4-pyridyl.
 2. The compound of claim 1 wherein said R₁ aryl, R₅ aryland R₆ aryl are independently phenyl, naphthyl or substituted phenyl. 3.The compound of claim 2 wherein said phenyl is substituted by halo,lower alkyl, nitro, amino, acylamino, hydroxyl, lower alkoxy,trifluoromethyl, alkyl sulfonyl, morpholinoethoxy ormorpholino-sulfonyl.
 4. The compound of claim 1 wherein said heteroarylis pyridyl, thienyl, furyl, thiozolyl, imidazolyl, pyrazolyl, triazinyl,quinolyl or isoquinolyl.
 5. A pharmaceutical composition for inhibitinginterleukin-1β protease comprising the formula (I) or a pharmaceuticallyacceptable salt thereof:

wherein R₁ is halogen, aromatic ether, alkyl sulfonate, aryl sulfonate,alkyl phosphonate, aryl phosphonate, alkyl phosphate or aryl phosphate;R₂ is OR₅, NH(CHR₅)_(m)—COOR₅, or NH(CHR₅)_(m)OH; R₃ is H or alkyl; R₄is H, substituted or unsubstituted aryl, heteroaryl or alkyl; R₅ and R₆are independently H, lower alkyl, aryl, hydroxy alkyl, amino alkyl,heteroaryl, lower alkylene-aryl, lower alkylene-heteroaryl or lowercycloalkyl; and m is 0–6 in a pharmaceutically acceptable carrier.
 6. Apharmaceutical composition comprising the compound of any one of claims1–4 or a pharmaceutically acceptable salt thereof.
 7. The pharmaceuticalcomposition of claim 6, wherein said composition is useful forinhibiting interleukin-1β protease.
 8. A method of inhibitinginterleukin-1β protease activity in a mammal in need of such treatmentcomprising administering to said mammal an effective inhibitory amountof a pharmaceutical composition comprising a compound of the formula (I)or a pharmaceutically acceptable salt thereof:

wherein R₁ is halogen, aromatic ether, alkyl sulfonate, aryl sulfonate,alkyl phosphonate, aryl phosphonate, alkyl phosphate or aryl phosphate;R₂ is OR₅, NH(CHR₅)_(m)—COOR₅, N(R₅)R₆ or NH(CHR₅)_(m)OH; R₃ is H oralkyl; R₄ is H, substituted or unsubstituted aryl, heteroaryl or alkyl;R₅ and R₆ are independently H, lower alkyl, aryl, hydroxy alkyl, aminoalkyl, heteroaryl, lower alkylene-aryl, lower alkylene-heteroaryl orlower cycloalkyl; and m is 0–6 in a pharmaceutically acceptable carrier.9. A method of treatment of a disease or disorder in a mammalcomprising: administering to said mammal the pharmaceutical compositionof claim 6, wherein the disease or disorder is rheumatoid arthritis.